Lead Dioxide (PbO2)-Powder

Characteristic

Lead(IV) oxide is the inorganic compound with the formula PbO₂. It is an oxide where lead is in an oxidation state of +4. It is a dark-brown solid which is insoluble in water. It exists in two crystalline forms. It has several important applications in electrochemistry, in particular as the positive plate of lead acid batteries.

Chemical formula：PbO₂

Molar mass：239.1988 g/mol

Appearance：dark-brown, black powder

Density：9.38 g/cm³

Melting point：290 °C (554 °F; 563 K) decomposes

Solubility in water：insoluble

Solubility：soluble in acetic acid，insoluble in alcohol

Refractive index (nD)：2.3

Crystal structure：hexagonal

Application

Lead dioxide is used in the production of matches, pyrotechnics, dyes and the curing of sulfide polymers. It is also used in the construction of high-voltage lightning arresters.

Lead dioxide is used as an anode material in electrochemistry. β-PbO₂ is more attractive for this purpose than the α form because it has relatively low resistivity, good corrosion resistance even in low-pH medium, and a high overvoltage for the evolution of oxygen in sulfuric- and nitric-acid-based electrolytes. Lead dioxide can also withstand chlorine evolution in hydrochloric acid. Lead dioxide anodes are inexpensive and were once used instead of conventional platinum and graphite electrodes for regenerating potassium dichromate. They were also applied as oxygen anodes for electroplating copper and zinc in sulfate baths. In organic synthesis, lead dioxide anodes were applied for the production of glyoxylic acid from oxalic acid in a sulfuric acid electrolyte.